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--- OpenXM/doc/issac2000/openxm-stackmachines.tex	1999/12/23 10:25:09	1.1
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-% $OpenXM$
+% $OpenXM: OpenXM/doc/issac2000/openxm-stackmachines.tex,v 1.11 2000/01/16 06:39:39 takayama Exp $
+
+\section{OpenXM Stack machines}\label{sec:ox-stackmachines}
+
+In OpenXM specification, all servers are stack machines.
+%These are called OpenXM stack machines.
+When a server ox\_xyz gets an OX data message,
+it translates the data into a local object of ox\_xyz
+and pushes the object onto the stack.
+According to the OpenMath specification, 
+the translation scheme 
+%% together with definitions of mathematical operations
+%% of the system ox\_xyz 
+is called the {\it PhraseBook} of ox\_xyz.
+For example, the Asir command {\tt ox\_push\_cmo(P,1)}
+(push integer $1$ onto the server $P$)
+sends an OX data message
+{\tt (OX\_DATA,(CMO\_ZZ,1))} to the server $P$.
+Here,
+{\tt OX\_DATA} stands for {\tt OX\_DATA} header and 
+{\tt (CMO\_ZZ,1)} is a body standing for $1$ expressed 
+by the CMO.
+The server tranlates {\tt (CMO\_ZZ, 1)} to its internal object of
+the integer  $1$
+and pushes the object onto the stack.
+
+If the server gets an {\it OX command} message, then the server 
+executes the command.
+Any OX command message starts with the int32 tag OX\_COMMAND.
+The body is a stack machine operation code expressed by int32.
+The codes are listed below \cite{noro-takayama}.
+\begin{verbatim}
+#define SM_popSerializedLocalObject               258
+#define SM_popCMO                                 262
+#define SM_popString                              263
+#define SM_mathcap                                264
+#define SM_pops                                   265
+#define SM_setName                                266
+#define SM_evalName                               267
+#define SM_executeStringByLocalParser             268
+#define SM_executeFunction                        269
+#define SM_beginBlock                             270
+#define SM_endBlock                               271
+#define SM_shutdown                               272
+#define SM_setMathCap                             273
+#define SM_executeStringByLocalParserInBatchMode  274
+#define SM_getsp                                  275
+#define SM_dupErrors                              276
+#define SM_control_kill                          1024
+#define SM_control_to_debug_mode                 1025
+#define SM_control_exit_debug_mode               1026
+#define SM_control_reset_connection              1030
+\end{verbatim}
+
+OpenXM does not have a standard for mathematical operation sets
+while it is a work in progress in the GAP group \cite{gap}.
+Each OpenXM server has its own set of mathematical operations,
+which are performed as follows.
+First, arguments for a mathematical operation
+and the number of the arguments are pushed.
+Second, 
+the mathematical operator name, 
+such as {\tt fctr} (the factorization command of Asir),
+is pushed as a string.
+Finally, the stack machine command
+{\tt SM\_executeFunction} (269) evaluates the operator and
+pushes the result onto the stack
+after poping the operator name, the number of arguments
+and arguments.
+For example, the following code factorizes $x^{100}-1$ by calling
+{\tt ox\_asir} from Asir.
+\begin{verbatim}
+P = ox_launch(); 
+ox_push_cmo(P,x^100-1); ox_push_cmo(P,ntoint32(1));
+ox_push_cmo(P,"fctr");  ox_push_cmd(P,269); 
+Ans = ox_pop_cmo(P);
+\end{verbatim}
+
+When an error has occurred on an OpenXM server,
+an error object is pushed onto the stack 
+instead of a result of the computation.
+The error object consists of the serial number of the OX message
+which caused the error, and an error message.
+\begin{verbatim}
+[340] P = ox_launch()$
+[341] ox_rpc(P,"fctr",1.2*x)$
+[342] ox_pop_cmo(P);
+error([8,fctr : invalid argument])
+\end{verbatim}
+
+OpenXM server won't send error messages to the client
+except when it receives a {\tt SM\_pop*} command.
+OX stackmachines work in the asynchronous mode which is similar 
+to X servers.
+For servers of graphic and sound applications, 
+it may be an advantageous feature.
+It is also possible to emulate RPC and a web server for MCP \cite{iamc} 
+on our asynchronous OX stackmachines.
+
+
+
+
+